| 
				 
					
						| Philips 
						A442 (straight version) |  |  
					
						| 
				
				
				Advertisement for the A442 radio valve in Radio Expres, 
				February 3rd, 1928 |    |   
				 Tetrode Introduced in 1927 
					
						
							| 1 | 2 | 3 | 4 | tc | base |  
							| g2 | f | f | g1 | a | B4 |    
				
					
						| Vf | Af | Va | Vs | Vg | mAa | mAs | Ra | gm |  
						| 4 | 0.06 | 200 | 100 | -1 | 4 | 0.8 | 400,000 | 0.7 |    
					
						| Equivalent | 1-442, 410SG, A2004, 
						C150, DZ2, G406, 
						G442, H406D, L409, PM14, RES094, RO4142, S4066, 
						S410, 
						SX406, TA42, VH300 |    |